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Posted By Topic: Removing PAT testing

thomas1237
Jan 11 2018 16:11

Working on a new industrial site where every single GPO circuit is connected via fixed RCBO in the switchboard, can we omit the PAT testing? Regulation 26 would suggest that the appliance is electrically safe. If we tested every RCBO every 12 months for operating time as 3760 requires, is this enough or is PAT testing every appliance still required?


   

pluto
Jan 11 2018 17:23

There some are of the opinion that when RCD protection on all socket outlets is provided, one has taken all reasonably präctical steps, then tag and test could be discontinued.

Internationally that opinion is also shared in the international standards, which by the way, do NOT provide for a Tag and Test system as detailed in AS/NZS 3760.
   

SteveH
Jan 11 2018 17:52

"Working on a new industrial site where every single GPO circuit is connected via fixed RCBO in the switchboard, can we omit the PAT testing? Regulation 26 would suggest that the appliance is electrically safe. If we tested every RCBO every 12 months for operating time as 3760 requires, is this enough or is PAT testing every appliance still required?"

What steps are going to be taken to ensure that items with guards and or interlocks are correctly guarded? Without details of the nature of operations, will items be brought onto the site that may not comply with NZ requirements? what process will detect those?

At the end of the day, whoever is in charge of the site can do (or not do) whatever they like, they just have to be prepared to "justify" what they have done/not done in the event that something goes pear shaped.

There are at least four possible scenarios where a correctly wired and functional RCD will not save someone from getting a lethal zap.

My suggestion would be to do a proper audit/risk assessment in accordance with AS/NZS ISO 31000 and bearing the E(S)Rs & H&S 2015 legislation, and see what you come up with
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Sarmajor
Jan 11 2018 19:21

You need to read ESR 26 again very carefully if you are thinking that you can rely on it for situation involving employees or contractors.

RCD's or RCBO's get you compliant with ESR 26 (1) but only for (b) & (c).

ESR 26 (2) makes it clear that the test and tag 3760 system gets you to deemed safe for ESR 26 (1) (a).

3760 is not the only way to get to deemed safe but it is the one mentioned in the ESR's and is therefore the default for now.
   

thomas1237
Jan 12 2018 08:08

"What steps are going to be taken to ensure that items with guards and or interlocks are correctly guarded? Without details of the nature of operations, will items be brought onto the site that may not comply with NZ requirements? what process will detect those?

At the end of the day, whoever is in charge of the site can do (or not do) whatever they like, they just have to be prepared to "justify" what they have done/not done in the event that something goes pear shaped.

There are at least four possible scenarios where a correctly wired and functional RCD will not save someone from getting a lethal zap.

My suggestion would be to do a proper audit/risk assessment in accordance with AS/NZS ISO 31000 and bearing the E(S)Rs & H&S 2015 legislation, and see what you come up with"

Thanks SteveH, I hadn't considered that guards could be removed from appliances, this could be controlled internally but my thoughts are now that any external contractors should have there tools tagged, which is standard throughout NZ anyway.Also agree about the risk assessment

The site is industrial and has loads of fix wired equipment, but every GPO circuit onsite is RCD protected.
   

thomas1237
Jan 12 2018 08:13

"There are at least four possible scenarios where a correctly wired and functional RCD will not save someone from getting a lethal zap"

Could you elaborate on this please
   

mowgli
Jan 12 2018 15:57

I can only think of three.

1. Casualty was medically compromised before receiving shock.
2. Shock path from active through casualty back to neutral.
3. Shock current outside RCD specification. Eg. type AC when shock current is pulsating DC.
4. Anybody's guess...
   

evanh
Jan 12 2018 16:54

For scenario #1, I'm assuming the RCD correctly operates and the received shock wouldn't have harmed a healthy person.

   

mowgli
Jan 12 2018 17:45

evanh yes. Some pre-existing medical condition.

I just thought of a fourth

4. fatal injury sustained as a consequence of a sub-lethal shock from an RCD. Falling from a ladder type of thing.
   

SteveH
Jan 12 2018 21:16

I can only think of three.

1. Casualty was medically compromised before receiving shock.
2. Shock path from active through casualty back to neutral.
3. Shock current outside RCD specification. Eg. type AC when shock current is pulsating DC.

You're on the money Rob, to this list you can add the following.

4. Shock is delivered to the victim at the start of the T wave portion of their heartbeat, this will instantaneously stop their heart even as the RCD opens. If the heart is stopped in this way, medical intervention required to restart.

5. Shock is received by victim that is over 50, your skin resistance decreases as you get over the 50(ish) speed bump, meaning a shock that might have just tickled you in your 20s,could be lethal after 50.

6. fatal injury sustained as a consequence of a sub-lethal shock from an RCD. Falling from a ladder type of thing.

So there are some possible scenarios to consider, and plan to mitigate Tom



   

evanh
Jan 13 2018 03:14

Yeah, and the roof could fall in too.

   

SteveH
Jan 13 2018 06:10

"Yeah, and the roof could fall in too."

If you are planning to step outside the "deemed safe" path, and go down the risk assessment route as per AS/NZS ISO 310000 Evan, then you are going to want to consider and plan for as many possibilities as your analysis uncovers.

Remember, the H&S landscape changed in 2015 (as a consequence of Pike River), companies are starting to be hammered with larger and steadily increasing penalties. So a belt & braces approach might be considered prudent.

Following the ChCh Earth Quakes,and the spotlight going on engineers etc, that thought things would be OK or "good enough" has seen a call for a corporate manslaughter to be brought in, so the consequences of any management decisions need to be considered carefully
   

evanh
Jan 13 2018 11:52

Watch out, that door handle is made of metal, it might have a sharp edge. Make sure you inspect it each time you go to open the door.


   

evanh
Jan 13 2018 11:54

And, of course, you're not the one qualified to remove the sharp edge so you're gonna have to report it for maintenance work to be done.


   

mowgli
Jan 13 2018 17:32

And absolutely don't go using the door handle while it's in an unsafe state. You'll have to walk the long way or delay the job indefinitely....
   

Andrew
Jan 15 2018 09:28

The key point is that an RCD tries to stop a shock being lethal, T&T tries to stop a shock occurring in the first place. As outlined, an RCD isn't foolproof (and anyway, a workplace that is happy to accept significant but non-fatal injury isn't my idea of a good workplace). T&T also isn't foolproof (even if it does get you to deemed safe), so a belt and braces approach is generally prudent as long as it's practical.